1. Field of the Invention
The present invention relates to an image positional relation correction apparatus for correcting the relative positional relation between a real image and a virtual image, a steering supporting apparatus provided with the image positional relation correction apparatus, and an image positional relation correction method.
2. Description of the Related Art
Conventionally, a steering supporting apparatus configured to show a rear image and a steering supporting guide on a monitor so that a steering wheel can be operated even if a driver cannot see a targeted position because a vehicle is in the driver""s blind spot. Such an apparatus is provided with a CCD camera for taking a real image of the rear of a vehicle, a monitor for showing an image taken by the CCD camera, a sensor for detecting information on a tire steering angle and the like, a circuit for providing a steering supporting guide as a virtual image for the purpose of providing a driver with appropriate steering information in accordance with the information from the sensor, and a circuit for display while superimposing the rear image of the vehicle and the steering supporting guide on a monitor screen.
Here, the CCD camera includes a lens and a CCD area sensor and is assembled in the state in which the optical axis of the lens and the center of the CCD area sensor are made coincide with each other, and, for example, a road 3 and a vehicle rear bumper 5 contained in the vehicle rear image, and a steering supporting guide 7 are displayed in an appropriate positional relation on a monitor screen 1 as shown in FIG. 10A in a normal state in which the CCD camera is mounted on the vehicle in a standard mounting position and angle. However, if the optical axis of the lens and the center of the CCD area sensor do not coincide with each other or if the CCD camera is not properly mounted on the vehicle as prescribed by the standard, as shown in FIG. 10B on the monitor screen 1, a vehicle rear image center 9 and a monitor screen center 11 for drawing the steering supporting guide 7 may not coincide with each other and the road 3 and the vehicle rear bumper 5, and the steering supporting guide 7 may shift from the appropriate positional relation.
In this case, the driver may not be able to back the vehicle as desired even if the driver moves the vehicle in accordance with the steering supporting guide 7. Therefore, the optical axis is usually adjusted so that the optical axis of the lens passes through the center of the CCD area sensor, that is, the relative positional relation between the CCD area sensor and the lens is adjusted. In addition, the mounting state of the CCD camera is adjusted for each individual vehicle so that the CCD camera is mounted on the vehicle as prescribed by the standard.
However, the above-mentioned adjustment of the optical axis is performed by physically adjusting the position of a lens at the time of fitting the lens. Therefore, it is difficult to perform the adjustment of the optical axis with high accuracy. In addition, there is a problem in that costs increase substantially if higher accuracy is sought.
Moreover, a lot of time is consumed in the adjustment work for mounting a CCD camera on a vehicle as prescribed by the standard. In addition, there is also a problem in that it is difficult to mount a CCD camera with high accuracy as prescribed by the standard, and that deviation arises in the actual state of mounting a CCD camera on a vehicle compared with the standard.
The present invention has been devised in view of the above and other drawbacks, and it is an object of the present invention to provide an image positional relation correction apparatus capable of properly correcting the positional relation between a real image and a virtual image without performing a physical optical axis adjustment, or without performing adjustment work for mounting a CCD camera on a vehicle as prescribed by the standard.
An image positional relation correction apparatus in accordance with the present invention is an image positional relation correction apparatus for correcting the relative positional relation between a real image taken by a camera and a virtual image superimposed to be displayed on a monitor screen together with the real image, which comprises real target providing means disposed in the object area of the camera for causing the camera to photograph a real target, virtual target providing means for providing a virtual target theoretically derived from the coordinates of the real target on the same coordinate system as the virtual image, and correcting means for correcting the relative positional relation between the real image and the virtual image based on the deviation of the real target and the virtual target.
In addition, a steering supporting apparatus in accordance with the present invention is provided with the image positional relation correction apparatus according to a first aspect of the present invention, wherein each of the real image and the virtual image is a rear image of a vehicle and a steering supporting guide.
Moreover, an image positional relation correction method in accordance with the present invention is an image positional relation correction method for correcting the relative positional relation between a real image taken by a camera and a virtual image to be superimposed to be displayed on a monitor screen together with the real image comprising the steps of taking a real target by a camera, setting a virtual target theoretically derived from the coordinates of the real target on the same coordinate system as the virtual image, and correcting the relative relation between the real image and the virtual image based on the deviation between the real target and the virtual target.